Dealkylation of alkylaromatic compounds



Aug. 23, 1966 H. s. BLOCH 3,263,610

DEALKYLATION OF ALKYLAROMATIC COMPOUNDS Filed Nov. 19, 1964 Fracl/onaf/on Zone Fracf/onaf/on Zone Dea/ky/a lion Zone I/V VE/V TOR- Herman S. Bloch A r TOR/VEYS' United States Patent 3,268,610 DEALKYLATIQN 0F ALKYLARQMATIC COMPOUNDS Herman S. Bloch, Skokie, IlL, assignor to Universai Oil Products Company, Des Plaiues, Hih, a corporation of Delaware Filed Nov. 19, 1964, Ser. No. 412,499 Claims. (Cl. 260-672) This invention relates to a process for the deaklylation of alkylaromatic compounds. More particularly, the invention is concerned with a process for the dealkylation of lower alkylaromatic hydrocarbons which contain at least one rat-hydrogen atom without the concomitant production of unwanted by-products.

Heretofore, various processes for the dealkylation of lower alkylaromatic hydrocarbons to produce desired aromatic hydrocarbons such as benzene and naphthalene have involved certain features which were undesirable from an economic standpoint. For example, certain dealkylation processes were either thermal or catalytic in nature. The thermal processes involved the use of extremely high temperatures which, of necessity, require expensive apparatus in which to operate. The catalytic dealkylation processes also involve relatively high temperatures.

Other drawbacks to these prior art processes involved the consumption of a considerable amount of hydrogen which had to be either manufactured at the site or purchased from an extraneous source and charged to the dealkylation process. Yet another drawback or disadvantage to the prior art processes involved the production of light paraffinic gases such as methane or ethane which possess a relatively low economic value, as a by-product of the process, which had to be vented or disposed of by the manufacturer of the aromatic hydrocarbon.

It is therefore an object of this invention to provide a novel process for the dealkylation of lower alkylaromatic hydrocarbons.

A further object of this invention is to provide a process for the dealkylation of alkylaromatic hydrocarbons without the consumption of hydrogen.

In a broad aspect one embodiment of this invention resides in a process for the dealkylation of an alkylaromatic hydrocarbon containing at least one tat-hydrogen atom on the alkyl radical which comprises passing said hydrocarbon to an alkylation zone, condensing said hydrocarbon with an alkylating agent in said zone in the presence of an alkaline catalyst at alkylation conditions, separating t-alkylaromatic hydrocarbon from nand secalkylaromatic hydrocarbons, recycling the latter hydrocarbons to said alkylation zone, passing said t-alkylaromatic hydrocarbon to a dealkylation zone, dealkylating said t-alkylaromatic hydrocarbon in the presence of an acidic catalyst at dealkylation conditions, and recovering the resultant aromatic hydrocarbon and isoolefin.

A further embodiment of this invention is found in a process for the dealkylation of an alkylaromatic hydrocarbon containing at least one tat-hydrogen atom on the alkyl radical which comprises passing said hydrocarbon to an alkylation zone, condensing said hydrocarbon with an olefin in said zone in the presence of potassium amide on a lithiated gamma-alumina support at a temperature in the range of from about 100 to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, separating t-alkylaromatic hydrocarbon from nand sec-alkylaromatic hydrocarbons, recycling the latter hydrocarbons to said alkylation zone, passing said t-alkylaromatic hydrocarbon to a dealkylation zone, dealkylating said t-alkylaromatic hydrocarbon in the presence of an acidic catalyst at a temperature in the range of from about 200 to about 350 C. and at "ice a pressure in the range of from atmospheric to about pounds per square inch, and recovering the resultant aromatic hydrocarbon and isoolefin.

A specific embodiment of this invention is found in a process for the dealkylation of toluene which comprises passing said toluene to an alkylation zone, condensing said toluene with ethylene in said zone in the presence of a catalyst comprising potassium amide on a lithiated gam- Ina-alumina support at a temperature in the range of from about 100 to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, separating t-heptylbenzene from n-propylbenzene and sec-pentylbenzene, recycling the latter alkylbenzenes to said alkylation zone, passing said t-heptylbenzene to a dealkylation zone, dealkylating said t-heptylbenzene in the presence of a silica-alumina catalyst at a temperature in the range of from about 200 to about 350 C. and at a pressure in the range of from atmospheric to about 100 pounds per square inch, and recovering the resultant benzene and 3-ethylpentenes.

Other objects and embodiments will be found in the following further detailed description of this invention.

As hereinbefore set forth, the present invention relates to a process for the dealkylation of alkylaromatic hydrocarbons which contain at least one u-hydrogen atom on the side chain without the consumption of a considerable amount of hydrogen and without the concurrent production of by-products which have either a relatively low economic value or are considered worthless in nature. In the present process the desired aromatic products, either monoor polycyclic in nature, such as benzene, naphthalene, anthracene, etc., are obtained by condensing an alkylaromatic hydrocarbon containing at least one u-hydrogen atom on the side chain with an alkylating agent, preferably an olefin such as ethylene, in the presence of an alkaline catalyst comprising an alkali metal amide disposed on a promoted metal oxide support. Relatively mild alkylating conditions comprising a temperature in the range of from about 100 to about 200 C. and a pressure in the range of from about 100 to about 2,000 pounds per square inch may be utilized. In addition, the mole ratio of alkylaromatic hydrocarbon to olefin should be in a range of from about 2 to about 10 moles of alkyl-aromatic hydrocarbon per mole of olefin. By utilizing such operating conditions, it is contemplated that a stable, continuous side-chain alkylation of the alkyl-aromatic hydrocarbon will result. The product resulting from this side chain alkylation is then passed to a fractionator wherein the desired product comprising talkylaromatic hydrocarbons will be recovered as the highest boiling product, while the lighter materials comprising unconverted primary alkylaromatic hydrocarbons, together with secondary alkylaromatic hydrocarbons which were initially present or are partial conversion products, are recycled to the alkylation zone for further condensation therein to thus prepare the desired t-alkylaromatic hydrocarbons.

The side chain alkylation of the alkylaromatic hydro carbons to form the desired t-alkylaromatic hydrocarbons is etfected in the presence of certain catalytic compositions of matter. Generically speaking, the catalyst which is used may be referred to as an alkaline catalyst. Specific examples of these alkaline catalysts comprise alkali metal oxides, alkali metal, alkoxides, hydroxides, borates, phosphates, carbonates, amides, and the like, disposed on a promoted metal oxide support; of these, the amides are preferred. The term promoted, as used hereinbefore and hereinafter in the specification and also in the appended claims, will refer to a pretreatment of the metal oxide support with a salt or hydroxide of a metal selected from the group including alkali metals and alkaline earth metals such as lithium, sodium, potassium,

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a rubidium, cesium, magnesium, calcium, strontium, and barium; Of the alkali metal amides which are composited or disposed on the promoted metal oxide support, potassium and sodium are preferred inasmuch as said metals exhibit substantially more activity than do other metals of the alkinous metal group (1.3., the group comprising alkali metals and alkaline earth metals) and potassium is especially preferred for the same aforesaid reason. In addition to their high activity, these two metals are preferred from an economic standpoint inasmuch as said metals are relatively more plentiful and correspondingly less expensive to use.

In preparing such catalysts, the alkaline component, preferably an alkali metal amide, is disposed on a support in a quantity ranging from about 2% to about or more by weight based on the support. The preferred supports which are utilized in the process of the present invention are those which are relatively or substantially free from water. In most cases, this freedom from water of the support is achieved by a precalcination treatment of said support. This precalcination is carried out at a relatively high temperature in the range of from about 400 to about 700 C. and for a time sufficient to effect substantial removal of absorbed or combined water from the support. The time required will vary, depending upon the support and, in addition, upon whether the water is in a combined or in merely a physically adsorbed form. In addition to the necessity for freed-om from water, the support is characterized by the necessity for having a high surface area. By the term high surface area is meant a surface area measured by surface adsorption techniques within the range of from about to about 500 or more square meters per gram and preferably a support having a surface area of approximately 100 to 300 square meters per gram. For example, it has been found that certain low surface area supports such as alpha-alumina which is obviously free from combined water and which has been freed from adsorbed water is not a satisfactory support for the alkali metal amides in the preparation of catalysts for use in the process of this invention. Alphaalumina is usually characterized by a surface area ranging from about 10 to about 25 square meters per gram. In contrast, gamma-alumina which has a surface area ranging from about 100 to about 300 square meters per gram, and which has been freed from adsorbed Water and which contains little combined water, is a satisfactory support. Celite, a naturally occurring mineral, after precalcination, is not a satisfactory support. Celite has a surface area of from about 2 to about 10 square meters per gram. Likewise, alkali metal amide dispersions on sand or on other low surface area silica are not satisfactory catalysts in this process. In addition, aluminas which contain combined water but which have relatively high surface areas are also not satisfactory supports. Such aluminas include dried alumina monohydrates which have not been sufficiently calcined to remove combined water and to form gamma-alumina. These alumina hydrates may have surface areas ranging from 50 to about 200 square meters per gram but because they contain combined water are not satisfactory supports. Particularly preferred supports for the preparation of catalysts for use in the process of this invention include high surface area crystalline alumina modifications such as gamma-, etaand theta-alumina, although these are not necessarily of equivalent suitability. However, as is obvious from the above discussion, the limitation of the use of any particular support is one of freedom from combined or adsorbed water in combination with the surface area of the support selected. In addition to the aforementioned types of support, another type is that which is prepared from an alkali alumina-te such as sodium aluminate, potassium aluminate, etc. from which a substantial majority of the alkali metal has been removed leaving only the alumina with a relatively minor amount of the alkali metal present.

The desired support, preferably, although not necessarily, gamma-, etc. or theta-alumina, is pretreated with a promoter in any manner. One method of impregnating the solid support is to treat said support with an alkali metal hydroxide such as lithium hydroxide, potassium hydroxide, sodium hydroxide, etc. and thereafter calcine at a temperature usually in the range of from about 500 to about 700 C. whereby said hydroxide is thoroughly dehydrated.

The catalyst which is preferably used in the process of the present invention is then prepared by dissolving an alkali metal such as potassium in liquid ammonia and impregnating the promoted alumina with an ammonia solution of potassium amide, the potassium amide having been formed when the potassium reacted with the ammonia. Following this impregnation by the alkali metal amide in the ammonia, the excess ammonia is driven off and the catalyst is then ready for use in the desired conversion reaction. Examples of alkali metal amides which may be utilized include potassium amide, sodamide, lithium amide, rubidium amide, cesium amide, the preferred amides comprising sodamide and potassium amide due to the relatively large amount of these metals available and the correspondingly lower cost of the same.

The t-alkylaromatic hydrocarbons which have thus been prepared are separated, as hereinbefore set forth, from unconverted primary alkylaromatic hydrocarbons and secondary alkylaromatic hydrocarbons, the latter two compounds being recycled or utilized as portions of the feed stock for the alkylation step. The t-alkylaromatic hydrocarbons are then subjected to dealkylation in the absence of any added hydrogen, said dealkylation being effected in the presence of an acidic catalyst at temperatures and pressures which are considerably lower than those which are utilized when dealkylating other alkylaromatic hydrocarbons in the presence of added hydrogen and other hydrodealkylation catalysts. For example, the dealkylating process of the present invention may be effected at temperatures ranging from about 200 to about 350 C. and at pressures ranging from atmospheric up to about pounds per square inch, any superatmospheric pressure being effected by the addition of an inert gas such as nitrogen. Examples of acidic catalysts which may be utilized comprise metal oxides and mixtures thereof such as silica-alumina, silica-alumina-magnesia, silica-aluminazirconia, acid-acting zeolites, montmorillonites, clays, etc. The products obtained by this dealkylation comprise the desired aromatic hydrocarbon as well as an isoolefin which may be utilized as an intermediate in the preparation of many useful organic compounds.

While the steps of this invention may be effected in either a batch or continuous type operation, the preferred method of effecting the dealkylation comprises a continuous method. In this respect the present invention will be further illustrated with reference to the accompanying drawing which illustrates a simplified flow diagram of a continuous method of operation for the dealkylation of alkylaromatic hydrocarbons according to the process of this invention. Various valves, condensers, pumps, controllers, knock-out pots, heating means, etc. have been eliminated as not being essential to the complete understanding of the present invention. The utilization of these, as well as other similar appurtenances, will become obvious as the drawing is described.

Referring now to the drawing, a charge stock comprising an alkylarom atic hydrocarbon containing at least one a-hydrogen atom on the side chain such as, for example, toluene, ethyl-benzene, n-propylbenzene, isopropylbenzene, l-methylnaphthalene, Z-methylnaphthalene, l-ethylnaphthalene, Z-ethylnaphthalene, etc., is charged to an alkylation zone 1 which is provided with the necessary heating means and which contains an alkaline catalyst of the type hereinbefore set forth in greater detail, said hydrocarbon being charged to the upper portion of zone 1 through line 2. An alkylating agent, preferably a low molecular weight olefin such as ethylene, is also charged to zone 1 through line 3, said al-kylation zone 1 being maintained at the necessary operating conditions of temperature and pressure. The reactor effluent is withdrawn from zone 1 through line 4, said etliuent comprising a mixture of t-alkylaromatic hydrocarbons, unconverted primary alkylaromatic hydrocarbons (if the feed aromatics were primary) and secondary alkylarornatic hydrocarbons. This mixture is passed to a fractionator 5 where the primary and secondary alkylaromatic hydrocarbons are withdrawn as overhead through line 6 and recycled to al kylation zone 1 wherein they undergo further condensation with the alkylating agent to form the desired t-alkylaromatic hydrocarbons. The higher boiling talkylaromatic hydrocarbons are withdrawn from fractionator 5 through line 7 and are passed to dealkylation zone 3 which contains an acidic catalyst of the type hereinbefore set forth in greater detail. This dealltylation zone is also maintained, by means of extraneous heating and pressure means, at the desired operating conditions of temperature and pressure. After passage through zone 8 the dealkylation efiiuent is passed through line 9 to fractionation zone 10. In fractionation zone .10 the desired products comprising the dealkylated aromatic hydrocarbons and the isoolefins are withdrawn overhead through line 11 to another fractionation zone 12, While the bottoms comprising alkylaromatic hydrocarbons which have not been dealkylated are recycled through line 13 back to dealkylation zone 8. In fractionation zone 12 the isoolefins and aromatic hydrocarbons such as benzene, naphthalene, etc., are separated; the lower boiling product is taken overhead through line 14 and passed to storage, While the higher boiling of the two products is also withdrawn as bottoms and passed to storage through line 15.

While the process of the present invention has been described as being operated in a continuous manner, it is also contemplated within the scope of this invention that the dealkylation of alkylarornatic hydrocarbons may also be effected in a batch type operation, although not necessarily with equivalent results. For example, a quantity of the alkylarornatic hydrocarbon such as toluene, methylnaphthalene, etc. may be charged to an appropriate apparatus such as, for example, a rotating autoclave which contains an alkaline catalyst of the type hereinbefore set forth. The autoclave is sealed and the alkylating agent such as ethylene is charged thereto. The autoclave is then heated to the desired temperature and maintained thereat for a predetermined residence time. At the end of this time the autoclave and contents thereof are cooled to room temperature, the excess pressure, if any, is vented and the autoclave is opened. Th reaction products are recovered, separated from catalyst and subjected to fractional distillation, usually under reduced pressure. The desired product comprising the t-alkylaromatic hydrocarbon is separated and placed in an ap propriate apparatus which contains an acidic dealkyla tion catalyst. This apparatus which may also comprise a rotating autoclave is then heated to the desired temperature and pressure and maintained thereat for a predetermined residence time. At the end of this time the autoclave and contents thereof are treated in a manner similar to that hereinbefore set forth and the desired products comprising the aromatic hydrocarbon and the isoole-fin are recovered by conventional means such as fractional distillation, crystallization, etc.

The following examples are given to illustrate the process of the present invention which, however, are not intended to limit the generally broad scope of the present invention in strict accordance therewith.

Example I In this example an alkylation catalyst is prepared by treating halide-free gamma-alumina spheres with lithium nitrate solution, calcining the promoted alumina at a temperature of about 550 C., slowly adding the promoted alumina to a flask in which ammonia is condensed and potassium has been slowly added in small increments, said flask being maintained at the reflux temperature of ammonia until the blue color has disappeared, the addition of the potassium to the condensed ammonia-being accomplished prior to the addition of the promoted alumina. The resulting mixture is continuously stirred and the ammonia is allowed to evaporate. The final catalyst will contain approximately t20% by weight of potassium amide calculated as potassium on the lithiated alumina base.

The catalyst is placed in a reactor comprising a stainless steel tube, said catalyst being loaded into th reactor under anhydrous conditions using high surface sodiumdried nitrogen as a blanketing gas. The catalyst is pretreated with nitrogen at an elevated temperature followed by pretreatment with toluene and thereafter with a solution of toluene in n-heptane. A feed stock comprising ethylene and toluene in a mole ratio of about 2 moles of toluene per mole of ethylene in a solvent comprising nheptane is charged to the reactor at a liquid hourly space velocity of about 2, said reactor being maintained at a temperature of about C. and a pressure of about 1,800 pounds per square inch. The reactor efiiuent is continuously withdrawn and passed to a fractionator. 'In the fractionator the cuts comprising n-propylbenzene and sec-pentylbenzene (as well as unconverted toluene and heptane) are separated and recycled to the reactor, while the cut comprising 3-phenyl-3-ethylpentane (theptylbenzene) is separated and passed to a dealkylation zone. This dealkylation zone also comprises a stainless steel tube containing a silica-alumina catalyst. The dealkylation zone is maintained at a temperature of about 250 C. and a pressure of about 50 pounds per square inch. The reactor eflluent is also continuously withdrawn from this dealkylation zone and passed to a second fractionator wherein benzene and B-ethyl-Z-pentene are separated by fractional distillation and recovered.

Example II A catalyst comprising approximately 20% by weight of potassium amide calculated as potassium impregnated on an alumina which is pretreated with lithium nitrate and calcined is placed in a reactor comprising a stainless steel tube under anhydrous conditions. The catalyst is pretreated with methylnaphthalene at an elevated temperature and pressure. Following the pretreatment of the catalyst, the feed stock comprising ethylene and methylnaphthalene in a mole ratio of about 3 moles of methylnaphthalene per mole of ethylene along with a solvent comprising n-decane is charged to the reactor at a liquid hourly spaced velocity of about 2:5. The reactor is maintained at a temperature of about .15 0 C. and a pressure of about 1,800 pounds per square inch. The reactor effluent is continuously withdrawn from the alkylation zone and passed to a fractionator where decane, unreacted methylnaphthalene, n-propylnaphthalene and secpentylnaphthalene are separated by fractional distillation under reduced pressure and recycled to the alkylation zone for further alkylation. The desired t-heptylnaphthalene is also separated by fractional distillation and passed to a dealkylation zone comprising a stainless steel tube which contains a silica-alumina catalyst. This zone is maintained at a temperature of about 250 C. and an imposed pressure of 75 pounds per square inch. After passage through the dealkylation zone the reactor effluent is withdrawn and passed to a second fractionator wherein the desired products comprising naphthalene and 3-ethyl- 2-pentene are separated and recovered.

Example III Other dealkylation reactions involving et'hylbenzene, npropylbenzene and isopropylbenzene '(cumene) wherein sald alkylarornatics are subjected to treatment similar to that set forth in the above examples utilizing ethylene as an alkylating agent in the presence of a catalyst comprising potassium amide composited on a lithiated gamma-alumina support and thereafter dealkylating the desired t-alkylaromatic hydrocarbons in the presence of an acidic catalyst will show similar results, that is, the obtention of benzene and the corresponding isoolefins namely, 3-methylpentene-2, 3-ethylpentene-2, and 2- methylbutene-2, respectively.

I claim as my invention:

1. A process for the dealkylation of an alkylaromatic hydrocarbon containing at least one rat-hydrogen atom on the side chain which comprises passing said hydrocarbon to an alkylation zone, condensing said hydrocarbon with an alk'ylating agent in said zone in the presence of an alkaline catalyst at alkylation conditions, separating t-alkylaromatic hydrocarbon from nand secalkylaromatic hydrocarbons, recycling the latter hydrocarbons to said alkylation zone, passing said t-alkylaromatic hydrocarbon to a dealkylation zone, dealkylating said t-alkylaromatic hydrocarbon in the presence of an acidic catalyst at dealkylation conditions, and recovering the resultant aromatic hydrocarbon and isoolefin.

2. A process for the dealkylation of an alkylaromatic hydrocarbon containing at least one ot-hydrogen atom on the side chain which comprises passing said hydrocarbon to an alkylation zone, condensing said hydrocarbon with an olefin in said zone in the presence of an alkaline catalyst at a temperature in the range of from about 100 to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, separating t-alkylaromatic hydrocarbon from nand sec-alkylarornatic hydrocarbons, recycling the latter hydrocarbons to said alkylation zone, passing said t-alkylaromatic hydrocarbon to a dealkylation zone, dealkylating said t-alkylaromatic hydrocarbon in the presence of an acidic catalyst at a temperature in the range of from about 200 to about 350 C. and at a pressure in the range of from atmospheric to about 100 pounds per square inch, and recovering the resultant aromatic hydrocarbon and isoolefin.

3. A process for the dealkylation of an alkylaromatic hydrocarbon containing at least one rat-hydrogen atom on the side chain which comprises passing said hydrocarbon to an alkylation zone, condensing said hydrocarbon with an olefin in said zone in the presence of an alkali metal amide on a promoted metal oxide support at a temperature in the range of from about 100 to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, separating t-alkylaromatic hydrocarbon from nand sec-alkylaromatic hydrocarbons, recycling the latter hydrocarbons to said alkylation zone, passing said t-alkylaromatic hydrocarbon to a dealkylation zone, dealkylating said talkylaromatic hydrocarbon in the presence of an acidic catalyst at a temperature in the range of from about 200 to about 350 C. and at a pressure in the range of from atmospheric to about 100 pounds per square inch, and recovering the resultant aromatic hydrocarbon and isoolefin.

4. A process for the dealkylation of an alkylaromatic hydrocarbon containing at least one u-hydrogen atom on the side chain which comprises passing said hydrocarbon to an alkylation zone, condensing said hydrocarbon with an olefin in said zone in the presence of potassium amide on a promoted metal oxide support at a temperature in the range of from about 100 to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, separating t-alkylaromatic hydrocarbon from nand sec-alkylaromatic hydrocarbons, recycling the latter hydrocarbons to said alkylation zone, passing said t-alkylaromatic hydrocarbon to a dealkylation zone, dealkylating said t-alkylaromatic hydrocarbon in the presence of an acidic catalyst at a temperature in the range of from about 200 to about 350 C. and at a pressure in the range of from atmospheric to about pounds per square inch, and recovering the resultant aro matic hydrocarbon and isoolefin.

5. A process for the dealkylation of an alkylaromatic hydrocarbon containing at least one tat-hydrogen atom on the side chain which comprises passing said hydrocarbon to an alkylation zone, condensing said hydrocarbon with an olefin in said zone in the presence of potassium amide on a promoted alumina support at a temperature in the range of from about to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, separating t-a1kylaromatic hydrocarbon from nand sec-alkylaromatic hydrocarbons, recycling the latter hydrocarbons to said alkylation zone, passing said t-alkylaromatic hydrocarbon to a dealkylation zone, dealkylating said t-alkylaromatic hydrocarbon in the presence of an acid catalyst at a temperature in the range of from about 200 to about 350 C. and at a pressure in the range of from atmospheric to about 100 pounds per square inch, and recovering the resultant aromatic hydrocarbon and isoolefin.

6. A process for the dealkylation of an alkylaromatic hydrocarbon containing at least one OL- hydrogen atom on the side chain which comprises passing said hydrocarbon to an alkylation zone, condensing said hydrocarbon With an olefin in said zone in the presence of potassium amide on a lithiated gamma-alumina support at a temperature in the range of from about 100 to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, separating t-alkylaromatic hydrocarbon from nand sec-alkylaromatic hydrocarbons, recycling the latter hydrocarbons to said alkylation zone, passing said t-alkylaromatic hydrocarbon to a dealkylation zone, dealkylating said t-alkylaromatic hydrocarbon in the presence of an acidic catalyst at a temperature in the range of from about 200 to about 350 C. and at a pressure in the range of from atmospheric to about 100 pounds per square inch, and recovering the resultant aromatic hydrocanbon and isoolefin.

7. A process for the dealkylation of an alkylaromatic hydrocarbon containing at least one whydrogen atom on the side chain which comprises passing said hydrocarbon to an alkylation zone, condensing said hydrocarbon with an olefin in said zone in the presence of potassium amide on a lithiated gamma-alumina support at a temperature in the range of from about 100 to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, separating t-alkylaromatic hydrocarbon from nand sec-alkylaromatic hydrocarbons, recycling the latter hydrocarbons to said alkylation zone, passing said t-alkylaromatic hydrocarbon to a dealkylation zone, dealkylating said t-alkylaromatic hydrocarbon in the presence of a silica alumina catalyst at a temperature in the range of from atmospheric to about 100 pounds per square inch, and recovering the resultant aromatic hydrocarbon and isoolefin.

8. A process for the dealkylation of an alkylaromatic hydrocarbon containing at least one a-hydrogen atom on the side chain which comprises passing said hydrocarbon to an alkylation zone, condensing said hydrocarbon with ethylene in said zone in the presence of potassium amide on a lithiated gamma-alumina support at a temperature in the range of from about 100 to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, sepa rating t-alkylaromatic hydrocarbon from nand sec-alkylaromatic hydrocarbons, recycling the latter hydrocarbons to said alkylation zone, passing said t-alkylaromatic hydrocarbon to a dealkylation zone, dealkylating said t-alkylaromatic hydrocarbon in the presence of a silicaalumina catalyst at a temperature in the range of from atmospheric to about 100 pounds per square inch, and recovering the resultant aromatic hydrocarbon and isoolefin.

9. A process for the dealkylation of toluene which comprises passing said toluene to an alkylation zone, condensing said toluene with ethylene in said zone in the presence of a catalyst comprising potassium amide on a lithiated gamma-alumina support at a temperature in the range of from about 100 to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, separating t-heptylbenzene from n-propylbenzene and sec-pentylbenzene, recycling the latter benzenes to said alkylation zone, passing said t-heptylbenzene to a dealkylation zone, dealkylating said t-heptylbenzene in the presence of a silica-alumina catalyst at a temperature in the range of from about 200 to about 350 C. and at a pressure in the range of from atmospheric to about 100 pounds per square inch, and recovering the resultant benzene and 3-ethyl-2-pentene.

10. A process for the dealkylation of methylnaphthalene which comprises passing said methylnaphthalene to an alkylation zone, condensing said methylnaphthalene with ethylene in said zone in the presence of a catalyst comprising potassium amide on a lithiated gammaalurnina support at a temperature in the range of from about 100 to about 200 C. and at a pressure in the range of from about 100 to about 2,000 pounds per square inch, separating t-heptylnaphthalene from n-propylnaphthalene and sec-pentylnaphthalene, recycling the latter naphthalenes to said alkylation zone, passing said t-heptylnaphthalene to a dealkylation zone, dealkylating said t-heptylnaphthalene in the presence of a silica-alumina catalyst at a temperature in the range of from about 200 to about 350 C. and at a pressure in the range of from atmospheric to about 100 pounds per square inch, and recovering the resultant methylnaphthaleneand 3-ethyl- 2-pentene.

References Cited by the Examiner UNITED STATES PATENTS 2,728,802 12/1955 Closson et al. 260-688 2,823,240 2/1958 Field et al. 260-688 3,006,976 10/1961 Shaw et a1. 260-688 3,128,318 4/1964 Meisinger et al 260-688 DELBERT E. GANTZ, Primary Examiner.

G. E. SCHMITKONS, Assistant Examiner. 

1. A PROCESS FOR THE DEALKYLATION OF AN ALKYLAROMATIC HYDROCARBON CONTAINING AT LEAST ONE A-HYDROGEN ATOM ON THE SIDE CHAIN WHICH COMPRISES PASSING SAID HYDROCARBON TO AN ALKYLATION ZONE, CONDENSING SAID HYDROCARBON WITH AN ALKYLATING AGENT IN SAID ZONE IN THE PRESENCE OF AN ALKALINE CATALYST AT ALKYLATION CONDITIONS, SEPARATING T-ALKYLAROMATIC HYDROCARBON FROM N-AND SECALKYLAROMATIC HYDROCARBON, RECYCLING THE LATTER HYDROCARBONS TO SAID ALKYLATION ZONE, PASSING SAID, T-ALKYLARMATIC HYDROCARBON TO A DEALKYLATION ZONE, DEALKYLATING SAID T-ALKTLAROMATIC HYDROCARBON IN THE PRESENCE OF AN ACIDIC CATALYST AT DEALKYLATION CONDITIONS, AND RECOVERING THE RESULTANT AROMATIC HYDROCARBON AND ISSOLEFIN. 